1. Field of the Invention
The invention relates to a switching device having a switching chamber, in which a stationary switching piece is arranged opposite to a moveable switching piece.
2. Description of the Related Art
Switching devices, such as heavy-duty contactors, in purely mechanical terms, are rated for a service life of 10 million switching cycles. If these contactors are used at their electrical design limit, the switching contacts will show wear far earlier, such as after 1 million switching cycles. Producers of high-cost, contactors already supply replacement switching pieces. A customer can then replace the worn switching pieces in the contactor, rather than replacing the complete high-cost contactor, thereby generating a cost saving.
However, the functionality of exchangeable switching pieces is subject to particular structural requirements. For example, arcing at the switching point, associated with a normal switching duty, results in the exceptionally high thermal loading of the switching chamber walls. Accordingly, for example, no thermoplastics can be employed in the vicinity of the switching point, as these will melt and may be damaged accordingly.
However, the use of thermoplastics for the switching chamber is a particularly attractive option, as the use of this special type of plastic permits the switching chamber to be configured with a more finely reticulated and smaller structure, thereby resulting in an overall contactor of more compact design.
Various switching devices with removable contact units are known from the prior art. EP 0 834 894 B2 discloses a switching device for an electric current, in which the switching arrangement is provided with a body of an electrically insulating material, and with a first and a second stationary contact, which are fitted to the body. The switching device is also provided with a moveable contact, which is movably coupled to the body and selectively engages with the first and second stationary contacts respectively to form an electrical connection. The switching device is also provided with an actuation arrangement incorporating a containment or a housing, which contains an electrically-actuated drive mechanism, and incorporating an element which is detachably coupled to the moveable contact, for the alternating actuation of the moveable contact such the latter is engaged with, or disengaged from the first and second stationary contacts.
Accordingly, the switching system is connected to the actuation system by a sealable arrangement, such that any arcs generated between the moveable contact and the first and second stationary contacts cannot escape from the electric current switching device, whereby the switching system is configured as an individual unit that can be detached from the actuation system for repair and replacement.
DE 1 094 851 discloses a contact device with an exchangeable contact unit is known, where the contact pieces of the electric power feed line are secured to a base unit, which is bonded to the contact unit such that, when the contact unit is removed from the base unit, it is not necessary to disconnect the power feed lines. In this arrangement, the exchangeable contact unit, which is preferably configured of a contact body with stationary contacts and an actuating element with moveable contacts, is mechanically secured to the base unit by detachable fastener that that cooperate with the contact pieces on the base unit. These fasteners simultaneously establish the electrical bonding of the contact unit with the power feed lines.
Conventional solutions have a disadvantage, in that they occupy a substantial unit volume and/or that the customer, at their own discretion, in addition to the switching pieces, is required to replace further individual components that can only be replaced by expert personnel.